1. Field of the Invention
The present invention relates to a control apparatus for a hybrid vehicle, and particularly relates to a control apparatus for hybrid vehicles, which is capable of recovering the charge-discharge balance by activating the motor during the travel when the charge-discharge balance of the battery device shifts to an over-discharge state.
2. Background Art
Hybrid vehicles provided with a motor in addition to an engine are conventionally known. There are two types of hybrid vehicles: series hybrid vehicles and parallel hybrid vehicles. Series hybrid vehicles are driven by a motor which is driven by a generator driven by the engine.
Since the motor is not connected mechanically to the engine, the engine can be driven at an approximately constant rotation speed within an speed region wherein the engine can be driven at a lower fuel consumption rate and lower emission rate than the case of a conventional engine.
In contrast, in parallel hybrid vehicles, a motor directly connected to the engine assists the engine in rotating the drive shaft, and the motor is used as a generator for charging electric energy into a battery device, and the electric energy generated by the motor is used for a variety of electric equipment in the hybrid vehicle.
Thus, in parallel hybrid vehicles, since the driving load of the engine can be reduced, the fuel consumption rate and the emission rate can be improved.
There are several types of the above-described parallel hybrid vehicle, one is a type in which the motor for assisting the output of the engine is directly connected to the engine axis, and the motor functions as a generator for charging the battery when the hybrid vehicle decelerates, and the other one is a type in which both or either one of the engine and the motor can generates the driving force and a generator is additionally provided.
In hybrid vehicles such as those described above, the demands of the driver can be satisfied by preserving the electric energy of the battery (hereinafter, called xe2x80x9cstate of chargexe2x80x9d, that is xe2x80x9cremaining battery chargexe2x80x9d) by carrying out a variety of controls so that the motor assists the engine at the time of acceleration, and the motor charges the battery by deceleration regeneration at the time of deceleration. For example, since a large amount of deceleration regeneration can be obtained after high speed travel, a part of the energy drawn from the battery can be recovered at the time of deceleration. That is, after climbing the uphill, the battery can be charged while travelling downhill (this technique is disclosed in Japanese Unexamined Patent Application, First Publication No. Hei 7-123509).
However, in conventional hybrid vehicles, when driven the hybrid vehicle without sufficient deceleration acceleration, the state of charge gradually decreases while driving the vehicle. Therefore, the problem arises that, when it is necessary to drive the car uphill, and subsequently drive on a flat road, the battery charge consumed at the time of driving the uphill can not be restored because no downhill regeneration is provided.
It is therefore an object of the present invention to provide a control apparatus for a hybrid vehicle, capable of charging the battery device when the driving conditions are such that the state of charge is decreasing rather than increasing, and when the state of charge has decreased by a predetermined amount from the initially read value.
According to the first aspect, a control apparatus for a hybrid vehicle is provided which comprises: an engine for outputting a driving force of the vehicle (for example, the engine E in the embodiment); a motor (for example, the motor M in the embodiment) for generating an auxiliary driving force for assisting the output of the engine; a battery device (for example, the battery 3 in the embodiment) for supplying electric power to the motor and for storing regenerative energy obtained by a regenerative operation of the motor at the time of supplying electric power to the motor during deceleration of the vehicle; an assist determination device (for example, step S005 in the embodiment) for determining whether it is necessary for the motor to assist the engine output in response to the driving conditions of the vehicle; an assist amount (for example, the final assist command value ASTPERF in the embodiment) determination device (for example, steps S209, S211, S216 in the embodiment) for determining the assist amount of the engine output by the motor in response to the engine driving condition when the assist of the engine output is determined by the assist determination device; an assist control device for assisting the output of the engine by the motor based on the assist amount determined by the assist amount determination device; wherein the control apparatus of the hybrid vehicle comprises: a travel start detecting device (for example, step S050 in the embodiment) for detecting the travel start of the vehicle; a state of charge (for example, SOC in the embodiment) detecting device (for example, the battery ECU 31 in the embodiment) for detecting the state of charge of the battery device; a discharge depth detecting device for detecting a discharge amount of the present state of charge (for example, the discharge depth DOD in step S063 in the embodiment) by comparison with the initial state of charge (for example, the initial value of the state of charge SOCINT in step S057 in the embodiment) detected at the time of starting the travel; a lower limit threshold value setting device (for example, step S060 in the embodiment) for setting the lower limit threshold value (for example, the lower limit threshold value SOCLMTL in step S060 in the embodiment) of the discharge amount based on the initial state of charge; an upper limit threshold value setting device (for example, step S061 in the embodiment) for setting the upper limit threshold value (for example, the upper limit threshold value SOCLMTH in step S061 in the embodiment) of the discharge amount based on the initial state of charge; a mode setting device (for example, step S054 in the embodiment) for changing the control mode of the motor when the state of charge of the battery device is reduced to the lower limit threshold value; and a mode setting release device (for example, step S062 in the embodiment) for releasing the setting of the motor control mode set by the mode setting device when the state of charge of the battery device reaches the upper limit threshold value; a determination threshold correction device (for example, step S103 provided with step S152, step S111 provided with step S162, step S123 provided with step S172 in the embodiment) for correcting the engine output determination threshold value (for example, the throttle assist trigger threshold value MAST, the suction pipe assist trigger threshold value MASTST, and the suction pipe assist trigger threshold value MASTTH in the embodiment) used as a standard for determination by the assist determination device in response to the discharge depth detected by the discharge depth detecting device when the motor control mode is changed by the mode setting device.
According to the above-described constitution, in the case of driving the hybrid vehicle by repeating sudden acceleration and sudden deceleration or in the case of driving climbing uphill and driving on a flat road subsequently without restoring the state of charge of the battery by the regeneration, the state of charge of the battery can be restored when the state of charge is decreasing and when the state of charge has decreased by a predetermined amount compared to the initial state of charge at the time of starting travel.
In addition, in the case of restoring the state of charge of the battery, a reduction in the state of charge of the battery can be recovered by reducing the frequency of the motor assist by raising the determination threshold value by the determination threshold value correction device depending on the discharge depth, and the state of charge of the battery can be restored rapidly when the state of charge is low.
According to the second aspect, the determination threshold value corrected by the determination threshold value correction device can be corrected based on the vehicle speed (for example, step S154 in the step S103, step S164 in the step S111, and step 174 in step S123 in the embodiment).
This correction process makes it possible to restore the state of charge of the battery by reducing the frequency of the assist operation by raising the determination threshold value, even when it is difficult to preserve the regeneration energy in the case of driving with repeated starts and stops during low speed travel in traffic congestion.
According to the third aspect, instead of using the determination threshold value correction device, it is possible to alternatively use the assist amount correction device (for example, step S219 in the embodiment), or the cruise generation amount control device (for example, step S307A in the embodiment) for correcting the charging amount (for example, the cruise generation amount CRSRGN in the embodiment) of the battery device during cruising.
In the above-described structure, the state of charge of the battery can be restored rapidly by setting a reduced assist amount by the assist amount control device or by setting an increased cruise generation amount by the cruise generation amount control device.
According to the fourth aspect, a control apparatus for a hybrid vehicle comprising an engine for outputting a driving force of the vehicle, a motor for generating an auxiliary driving force for assisting the output of the engine, a battery device for supplying electric power to the motor and for storing regenerative energy obtained by a regenerative operation of the motor at the time of supplying electric power to the motor during deceleration of the vehicle, an assist determination device for determining whether it is necessary for the motor to assist the engine output in response to the driving condition of the vehicle, an assist amount determination device for determining the assist amount of the engine output by the motor in response to the engine driving conditions when an assist of the engine output is determined by the assist determination device, an assist control device for assisting the output of the engine by the motor based on the assist amount determined by the assist amount determination device, wherein the control apparatus of the hybrid vehicle comprises a travel start detecting device for detecting the travel start of the vehicle, a state of charge detecting device for detecting the state of charge of the battery device, a discharge depth detecting device for detecting a discharge amount of the present state of charge by comparison with the initial state of charge detected at the time of starting the travel, a step (for example, step S060 in the embodiment) for setting a discharge amount with respect to the initial state of charge, a step (for example, step S061 in the embodiment) for setting a charge amount with respect to the initial state of charge, a mode setting device for changing the control mode of the motor when the state of charge of the battery is reduced to the discharge amount, a mode setting release device for releasing the setting of the motor control mode changed by the mode setting device when the state of charge of the battery device reaches the upper limit threshold value, and a determination threshold correction device for correcting the engine output determination threshold used as a standard for determination by the assist determination device corrects in response to the discharge depth detected by the discharge depth detecting device when the motor control mode is changed by the mode setting device.
According to the fifth aspect, in the above control apparatus for a hybrid vehicle, the determination threshold corrected by the determination threshold correction device is corrected in response to the vehicle speed.
According to the sixth aspect, in the above control apparatus for a hybrid vehicle, the control apparatus comprises, in place of the determination threshold correction device, an assist amount correction device for correcting an assisting amount for driving the engine or a cruise power-generation correction device for correcting a charge amount to the battery device while the vehicle travels in the cruise mode.
According to the seventh aspect, in the above control apparatus for a hybrid vehicle, a corrected value of the determination threshold is added to the determination value (for example, steps S152, S162, and S172 in the embodiment) used as a standard corrected in response to the discharge depth.
According to the eighth aspect, in the control apparatus for a hybrid vehicle, the value in response to the discharge depth is corrected by the vehicle speed (for example, steps S154, S164, and S174 in the embodiment).
According to the ninth aspect, the above control apparatus for a hybrid vehicle, in the throttle assist trigger correction, the throttle assist trigger value is corrected in response to the discharge depth (for example, steps S152 and S155 in the embodiment).
According to the tenth aspect, in the above control apparatus for a hybrid vehicle, the corrected value according to the discharge depth is corrected (for example, steps S154 and S155 in the embodiment)in response to the vehicle speed.
According to the eleventh aspect, in the above control apparatus for a hybrid vehicle, in a suction pipe negative pressure assist trigger correction, the suction pipe negative pressure assist trigger is corrected in response to the discharge depth (for example, step S162, S165, S172, and step S175 in the embodiment).
According to the twelfth aspect, in the above control apparatus for a hybrid vehicle, the correction executed in response to the discharge depth is further corrected in response to the vehicle speed (for example, step S164, S165, S174, and S175).
According to the thirteenth aspect, in the above control apparatus for a hybrid vehicle, the amount of charge to the battery device at the time of driving in the cruise mode is corrected by the discharge depth.